1. Field of the Invention
The present invention relates to laboratory safety enclosures for use in handling biohazard materials, and in particular to laboratory safety enclosures for use in housing automated instrumentation used in the handling of biohazard materials.
2. Description of the Prior Art
Laboratory safety enclosures, also known as vented workstations, are safety devices used in research, analytical, teaching, and other laboratories. These containment devices provide enclosed work areas where handling of toxic substances can be performed with minimum risk to users. They are used primarily in pharmaceutical, chemical, biological and toxicological laboratory settings.
Specifically, a laboratory safety enclosure is comprised of a work chamber within which materials are manipulated or worked upon by an operator, a means for introducing uncontaminated air into the chamber, an air exhaust mechanism for removing contaminated air from the enclosure, and a means such as a HEPA filter for removing hazardous contaminants from the air before exhausting the air from the workstation, or returning the air to the work chamber.
The enclosure is comprised of a work chamber with an access opening and an exhaust or discharge opening. The enclosure may include a pair of spaced, parallel side walls; rear and upper walls joining the side walls; and a bottom wall or floor that together define the work chamber. The chamber also has an access opening or inlet through which the operator inserts, removes or manipulates material within the chamber. Exterior air, i.e., air from outside the workstation, can enter the chamber through this access opening. In some workstation designs a top or bottom bypass is also provided for this purpose. A moveable closure can be employed to vary the size of, or close, the access opening. Air is exhausted from the work chamber through an opening that may be located on the opposite side of the chamber from the access opening.
Air exhausted from the chamber may be discharged to the atmosphere, i.e., to the exterior of the workstation, such as into the room where the workstation is located, or outside the building. Before being discharged, the air is directed through a HEPA filter to remove contaminants. Instead of discharging the air to the atmosphere, a part or all of the air may be returned to the work chamber after passing through the HEPA filter.
In designing a workstation, one of the primary goals is to minimize turbulence of the airflow. The resulting laminar flow structure promotes containment efficiency without affecting balance readings, dispersing light powders or otherwise compromising process efficiency. In addition, laminar airflow across the work chamber avoids “dead spots” or stagnant areas where contaminated air can reside without being exhausted from the chamber.
In a conventional laboratory workstation, the chamber is configured with the access opening, and optionally air inlets, at the front of the chamber, and exhaust openings in the bottom and/or rear of the chamber. If a part of the exhausted air is to be filtered and returned to the work chamber, a return inlet is normally provided in the upper wall of the chamber. This configuration is suitable for workstations in which an operator manipulates small volumes of material through the access opening. However, many laboratory and manufacturing procedures now require isolation from the environment of automated instrumentation that is simply too large to conveniently fit within a conventionally designed workstation, while still achieving the desired non-turbulent airflow.